Comparative digestive biology between the ponyfishes from the Pranburi River estuary,Thailand

We investigated the digestive biology of two prevalent leiognathid species in Pranburi River estuary, Thailand: the decorated ponyfish (Nuchequula gerreoides) and the splendid polyfish (Eubleekeria splendens). A total of 632 samples collected from February to April and September to November 2017 were analysed using morphological and histological approaches. The overall structures were similar between the species: a short mucous-cell-rich oesophagus region, a well-developed gastric gland uniformly present across the stomach's mucosal layer, and three finger-like pyloric caeca between the stomach and intestine. However, there were marked differences in the mouth, gill raker, and intestinal coefficient (IC). N. gerreoides had a relatively longer mouth, smoother gill rakers, and an IC of 1.08 ± 0.01, similar to those of other carnivorous fish. In contrast, the gill raker of E. splendens had more villiform teeth that can filter-feed better, and their IC was 2.16 ± 0.02 (i.e., longer intestine). Although digestive structures were generally similar between the ponyfishes, these differences suggest that N. gerreoides is relatively carnivorous with stronger suction, whereas E. splendens may be an omnivorous or herbivorous filter-feeder.     

Succinoxidase Activity of Avocado Fruit Mitochondria in Relation to Temperature and Chilling Injury throughout the Climacteric Cycle

Mitochondria were isolated from `Fuerte' avocado fruit (Persea americana Mill.) at four different stages of the respiratory climacteric. Preclimacteric fruit had the highest rate of succinate oxidation and the postclimacteric mitochondria the lowest. Subsequently, successive additions of ADP increased the respiratory control ratio.     

Ethylene production in relation to the initiation of respiratory climacteric in fruit

Respiration of cherimoya fruit shows two peaks of CO₂ production.The IEC is less than 0.05 ppm until the midpoint of the firstrespiratory rise. The fruit softens, develops pleasant aromaand flavor, and is considered ripe at the beginning of the secondrespiratory rise. Ripening and CO₂ production in cherimoya andavocado fruit are initiated with no increase of internal ethyleneand at ethylene levels which do not normally induce ripeningin fruit. The ratio of the internal concentration of ethylene to its productionrate varied with the stage of the climacteric and was less thanone except for the very early stage in cherimoyas. ¹Present address: Dept. of Plant Sciences, Kasetsart Univ.,Bangkok, Thailand. (Received February 6, 1975; )